Abstract: Recycled construction waste mixed sand was obtained by mixing recycled concrete coarse sand, recycled brick coarse sand and ultra fine sand. The effect of the recycled aggregate replacement ratio, the water-binder ratio and the fly ash replacement ratio on the performances of recycled mortar is researched. By analytic hierarchy process, variance analysis and the method of synthetically judgment，the optimal proportion was obtained. The results show that the water-binder ratio and the fly ash replacement ratio are the key factors for the performances of recycled mortar. The increasing of fly ash replacement ratio has negative effect on recycled mortar strength. The recycled aggregate replacement ratio has a significant impact on consistency and minimal impact on compressive strength and bending strength.